It is widely performed to cool or heat a heat-exchange target by passing a flow of the heat-exchange target through a pipe made of a material having a high thermal conductivity, while brining a cooling medium or a high-temperature fluid into contact with an outer periphery of the pipe. It is also commonly performed to heat a material as a heat-exchange target to a temperature for efficiently performing processing or treatment thereof, and then subject the heated material to the processing or treatment.
Meanwhile, when producing a polymer product such as polyethylene or polypropylene, e.g., when producing polyethylene by inducing, in a polymerization reactor, a reaction between a catalyst and ethylene dissolved in a solvent such as n-hexane, the resulting polyethylene as a polymer product adheres to an inner wall of the polymerization reactor. Further, when transporting, under cooling, a mixed solution of the polymerization product and the solvent from the polymerization reactor to a post-processing apparatus such as a pelletizer, a phenomenon that the polymer product precipitates and adheres to an inner wall of a means for the transport occurs to form so-called “polymer fouling”.
Moreover, in the polymerization of polyethylene or the like, there is a problem that reaction heat is generated in the polymerization reactor through the polymerization reaction. If this reaction heat is not efficiently removed, i.e., cooling is not efficiently performed, running conditions for the polymerization reactor cannot be controlled, thereby possibly causing a situation where physical properties of a polymerization reaction product are significantly changed and thus the polymerization reactor is forced to be shut down.
For removing the above reaction heat, there are some cases where a shell-and-tube heat exchanger is provided in the inner wall of the polymerization reactor, and the transport means for transporting, under cooling, the solution from the polymerization reactor to the post-processing apparatus such as a pelletizer. In these cases, a polymer fouling is formed on inner walls of a plurality of metal tubes for separating the polymer contained in the solvent from a coolant, in the shell-and-tube heat exchanger.
This polymer fouling causes significant deterioration in removal of the reaction heat, i.e., cooling, because it has a thermal conductivity which is less than that of the metal tube by about two digits. At the same time, a substantial tube diameter of each of the metal tubes becomes smaller, thereby causing negative effects, such as an increase in load of a transport pump, damage to transport pump, and deterioration in production efficiency due to a decrease in flow rate.
With a view to preventing the formation of and buildup of a polymer fouling, there have been proposed the following measures:                (1) Increasing a flow velocity in a reactor and a transport tube;        (2) Minimizing irregularities in an inner surface of each of the reactor and the transport tube;        (3) Adding an electrostatic remover based on a technical analysis indicating that an origin of the polymer fouling is electrostatic adhesion of catalyst and polymer particles;        (4) Improving a structure of an ethylene feed nozzle;        (5) Providing an improved structure capable of preventing the polymer from stagnating around a gap between flanges and the like (See, for example, the following Non-Patent Document 1).        
Further, as one conventional means to prevent the formation of a polymer fouling, there has been proposed a technique of adding an anti-fouling agent to a composition of a solution of a polymer dissolved in a solvent, in a polymerization apparatus or a subsequent process, wherein the anti-fouling agent contains a polyoxyalkylene-based polymer having a number average molecular weight of 30000 or less and represented a specific general formula (see, for example, the following Patent Document 1).
As another conventional means to prevent the formation of a polymer fouling, there has been proposed an olefin polymerization method capable of preventing clogging of a line for supplying catalyst slurry to a polymerization reactor to enable continuous running of a polymerization reactor, wherein, when supplying catalyst slurry containing a pre-polymerization catalyst supported on a solid, to a gas-phase reactor for performing a final olefin polymerization, the catalyst slurry is accompanied by 0.3 to 3.0 mg of an organic aluminum compound with respect to 1 g of the pre-polymerization catalyst (see, for example, the following Patent Document 2).
As yet another conventional means to prevent the formation of a polymer fouling, there has been proposed a heat transfer device 10 for heating or cooling a process stream having an inner surface and an outer surface, to provide resistance to corrosion and corrosion-induced fouling, to a metal tube heat exchanger exposed to the process stream at high temperatures, wherein the heat transfer device 10 is a tube formed of a steel alloy comprising X, Y, and Z, wherein the tube comprises three layer consisting of: a substrate layer made of a steel alloy having an arithmetic average roughness of less than 40 micro inches (1.1 μm); a chromium enriched oxide layer formed on at least one of the inner surface and the outer surface, wherein the chromium enriched oxide layer contains 10 to 40 weight % of chromium; and a surface protective layer formed on the chromium enriched oxide layer, wherein the surface protective layer contains sulfide, oxide, oxysulfide or a mixture thereof (see, for example, the following Patent Document 3).
The above conventional techniques are incapable of effectively preventing or reducing the formation of a polymer fouling to an extent that they satisfy industrial requirements. Therefore, still other measures or techniques have been proposed. Specifically, there has been proposed a technique of adhering and forming a thin film onto an inner wall of a metal pipe, wherein the thin film is capable of being removed by chemical liquid or desired gas (see, for example, the following Patent Document 4).
As another further conventional means to prevent the formation of a polymer fouling, there has been proposed a scale removal method which comprises performing a chemical operation or a physical operation using a container having a resin film formed on an inner wall thereof, and then removing a scale produced on the resin film on the inner wall of the container during a process of the operation, together with the resin film (see, for example, the following Patent Document 5).
As still a further conventional means to prevent the formation of a polymer fouling, there has been proposed an installation method for a piping inner tube to be installed inside a pipe for sending a liquid or paste-form fluid, wherein the method comprises: penetratingly placing the tube inside the pipe; closing one of opposite edges of the tube and sending gas from the other edge into the tube to thereby expand the tube and bring the tube into close contact with an inner surface of the pipe; and fixing opposite ends of the tube to respective ends of the pipe while keeping the ends of the tube in close contact with the respective ends of the pipe (see, for example, the following Patent Document 6).